Geared pump

ABSTRACT

The invention relates to a gear pump of the type having internally and externally toothed, eccentrically disposed members which rotate about their respective axes. The gear pump incorporates a centering device for centering housing elements of the pump during the assembly operations which comprises bores of different diameters in adjacent housing parts and a ball which is press fitted in the bore of larger diameter and has contact with the circular edge of the bore of lesser diameter.

United States Patent Inventors Gunnar Lyshoj Hansen;

Jorgen Hartvig Petersen, both of Nordborg, Denmark Appl. No. 842,125

Filed July 16, 1969 Patented June 15, 1971 Assignee A.'S. Danfoss Nordborg, Denmark July 12, 1968 Germany Priority GEARED PUMP 4 Claims, 3 Drawing Figs.

U.S. Cl

418/171, 418/270 Int.Cl F01c l/l0,

F04c 1/06, F04c 17/06 [50] Field of Search 418/70, 171,270, 107, 108; 103/126; 230/141; 123/12; 285/2729; 91/63 [56] References Cited UNITED STATES PATENTS 3,137,234 6/1964 Mosbacher 103/126 A 3 ,484,142 12/1969 Nishiwaki 308/74 Primary Examiner-Carlton R. Croyle Assistant Examiner-John J. Vrablik Attorney-Wayne B. Easton ABSTRACT: The invention relates to a gear pump of the type having internally and externally toothed, eccentrically disposed members which rotate about their respective axes. The gear pump incorporates a centering device for centering housing elements of the pump during the assembly operations which comprises bores of different diameters in adjacent housing parts and a ball which is press fitted in the bore of larger diameter and has contact with the circular edge of the bore of lesser diameter.

PATENTEU JUN} 5197:

GEARED PUMP The invention relates to a geared pump comprising an externally toothed wheel and an internally toothed ring, guided in a circular cutaway portion in a housing ring, which both rotate about their own axes, but the one being offset from the other, the housing ring being mounted on a part of the housing by means of a centering device and being secured thereto by means of screws.

Geared pumps of this kind are known in which a housing part, through which the drive shaft passes, the housing ring and a housing cover, fitted at the opposite end, are firmly interconnected by means of screws. The screws extend through relatively large holes in the housing ring, so that the latter can, before the screws are tightened, be accurately aligned in relation to the shaft bearing in such manner that the two toothed elements can rotate smoothly despite their axes being mutually offset. In order to facilitate the alignment, a stud is provided on one side of the end face of the housing ring, which stud extends into a bore in the contiguous part of the housing and thus limits the aligning movement to a rotary movement.

In a centering device of this kind, the dimensions of the stud and the bore must be accurately matched since otherwise there would be play. which would cause doubt as to whether proper centering was achieved. If the axis ofthe stud and/or of the bore is not precisely at right angles to the end face, there arises the risk of the two end faces not being absolutely parallel with each other, and this parallel position is essential both as regards sealing and the smooth running of the toothed elements. Moreover, care must be taken that there is no burr in or around the hole since this too will prevent the surfaces from lying against each other n a precise manner.

The object of the invention is to provide a simple play-free centering device which ensures that the faces of the two housing elements lie against each other in a flat and parallel manner.

According to the invention this object is achieved by means of a sphere which is held in the first housing element in such a way that it can be forced into its holder, and by means of hole in the second housing element, the free end edge of which has a diameter smaller than the diameter of the sphere.

In this arrangement, the second housing element, bearing on the sphere by the end edge, can be swung as required and therefore positioned with its end face parallel with the end face of the first housing element. Since the sphere can be forced into its holder this enables the free end edge of the hole to correspond precisely to the diameter of the bearing circle on the sphere when the two housing elements lie against each other, and a play-free fit is therefore ensured. Neither effect is adversely influenced by lack ofprecision in making the hole or the sphere-holder (inclined axis, large tolerances and so on). Moreover, any burr present is pressed in by the sphere being forced into the holder and into the hole, so that no special deburring operation needs to be carried out.

Assembly can be of a very simple kind. Thus, in a method for producing the geared pump, the invention provides for the sphere firstly being pressed into the holder only to an extent such that it is brought into its final position only when the housing elements are pressed against each other. The second housing element is thus used as a pressure-applying member. Consequently, a play-free fit is ensured in the final position.

Expediently, the pressing together is achieved simply by tightening the screws. There is no difficulty in so rating the force used for pushing the sphere that this force can be applied with the help of the screws.

In a preferred embodiment, the holder in the first housing element consists 'of a bore having a somewhat smaller diameter than the diameter of the sphere. Furthermore, the hole in the second housing element can consist of a bore having a diameter smaller than the diameter of the bore in the first housing element. The production of the centering device therefore merely entails making the two bores and pressing in the sphere.

Preferably, the circle of contact between the end edge of the hole and the sphere is such' that the radius running to the center of the sphere forms an angle of more than 60 but less than with the axis of the hole. In this way the sphere can be wedged into the hole and this facilitates the provision of the play-free retaining arrangement. Additionally, a relatively large area of contact with the sphere is obtained by only slightly deforming the circumference of the hole near its end edge.

This centering device is suitable for a in variety of purposes. If the initially described centering device has to be replaced, it is of advantage to fit a single centering sphere on one side on the surface of contact between the housing ring and the end wall of the housing through which the shaft passes, and to create a pivotal point. In particular, the ball can be fitted on a line which runs roughly at right angles to the line connecting the axes of the two toothed elements. By rotating this sphere, the distance between the two toothed elements can be altered in the correct direction.

In this connection, it is particularly advantageous if the housing elements are firstly loosely screwed together, the pump then started up and the screws tightened while the pump is running. Since, due to the sphere, the housing ring is free to move only in one direction, it adjusts itself accurately to the correct position when the pump is running.

The centering device can, however, also be used for other purposes. For example, at least two centering spheres can be provided on the surface of contact between the housing ring and a cover applied to that end opposite the end wall of the housing and provided with supply and discharge passages. The position of the housing ring and the cover can be accurately fixed by means of two such spheres. Consequently, the supply and discharge passages can be adapted with greater accuracy to the position of the chambers between the toothed elements. Hitherto, the cover has been centered only by means of the screws.

Furthermore, the holders for the spheres should be provided in the housing ring. After dismantling the pump, a housing ring that can be produced in a very simple manner, can be exchanged and when the pump is put together again, play-free centering can be carried out.

It is also expedient for the bores in the housing ring to pass right through it. These bores can be easily made Furthermore, during a repair operation, the spheres can be knocked out and replaced, for example, by spheres of a somewhat greater diameter.

The invention will now be described in more detail by reference to an embodiment illustrated in the drawing, in which:

FIG. 1 illustrates a geared pump of the invention in side elevation and partly in section on the line A-A of FIG. 2,

FIG. 2 is a section on the line B-B OF FIG. 1, and

FIG. 3 is a sectional illustration, on a larger scale, of the centering device.

The geared pump illustrated has a housing part 1 which incorporates the bearing for a drive shaft 2, a housing ring 3 and a housing cover 4, which are interconnected by screwbolts 5. The screwbolts extend loosely through holes 6 in the housing ring 3 and the cover 4. An externally toothed wheel 7 is fitted on the shaft 2. Mounted in a circular cutaway portion 3 in the housing ring 3 is an internally toothed ring 9 having one tooth more than the wheel 7. The housing part 1, the cover 4 and the toothed elements 7 and 9 form pump chambers 10, which increase in size at each revolution and then diminish in size again. The chambers 10 are supplied through passages 11 in the cover which are only shown schematically. The axis l2 of the cutaway portion 8 and thus of the toothed ring 9 is offset from the axis I3 "of the shaft '2 and therefore of the toothed wheel 7.

Fitted between the housing part 1 and the housing ring 3 is a centering device 14 illustrated in more detail in FIG. 3. The housing ring 3 contains a straight-through bore l5, and the housing part 1 a bore 16 closed at one end. Also, there is provided a sphere 17, the center 18 of which is located at a little distance inside the housing ring 3. The diameter of the bore 15 is somewhat smaller than the diameter of the sphere 17, for example onetenth/two-tenths of a millimeter smaller. The sphere 18 therefore sits firmly in the bore 15, but can be pushed into it when force is applied thereto. The diameter of the bore 16 is somewhat smaller than that of the bore 15, for example one-tenth/two-tenths of a millimeter smaller. Consequently, there is a line of contact between the end edge of the bore 16 and the sphere 17 that extends along a circle which has a smaller diameter than the sphere. The angle between a radius running to the center of the sphere and the axis of the centering device is greater than 60 but less than 90. in this arrangement, no damage is caused if the contacting end edge is deformed somewhat by the sphere or if, due to widening at the open end of the bore 16, it is set back somewhat from the surface of contact between the parts 1 and 3.

Two similar centering devices 20 and 21 are fitted between the housing ring 3 and the cover 4, the bore of greater diameter again being provided in the housing ring. The position of the two centering devices is shown in broken lines in FIG. 2. The position of the cover 4 relatively to the ring 3 is accurately fixed by these two centering devices The procedure in assembly is that firstly three spheres 17 are pressed lightly into their associated bores 15. The pump is then fully assembled but the screwbolts 5 are only slightly tightened. After this, the pump shaft 2 is driven, the precisely correct distance between the axes 12 and 13 being set, since the ring 3 can rotate only about the centering device 14. While the pump is running, the screwbolts 5 are tightened. When this happens, the spheres 17 are pushed through the end edges of the bore 16 so far into the bores that when the housing elements lie against each other accurate, play-free contact is achieved. Finally, the whole assembly can be sealed by a cover 22.

We claim:

1. A gear pump comprising first and second housing members having flat surfaces in abutting engagement in a plane, said first member having a circular cutout, an externally toothed wheel, an internally toothed wheel in eccentrically disposed and in surrounding relation to said externally toothed wheel, said internally toothed wheel having a circular periphery and being rotatably disposed in said cutout, said wheels being rotatable about their respective axes to form expanding and contracting chambers, a centering device comprising a first cylindrical bore in said first member, a sphere having a slightly larger diameter than said first bore being press fitted into said first bore, said first bore having a depth substantially larger than the diameter of said sphere, a second cylindrical bore in said second member having a smaller diameter than said first bore and having a circular edge thereof in said plane and in contact with said sphere, and fastening means for holding said members in abutting engagement.

2. A gear pump according to claim 1 wherein a radius from the center of said sphere to said circular edge is between 60 and relative to the axis of said second bore.

3. A gear pump according to claim 1 in which said sphere forms a pivoting point for relative pivotal movement between said members prior to said fastening means being applied.

4. A gear pump according to claim 1 wherein said sphere is disposed on a first line which is substantially normal to a second line which extends through said axes, said first line intersecting said second line in the vicinity of said axes. 

1. A gear pump comprising first and second housing members having flat surfaces in abutting engagement in a plane, said first member having a circular cutout, an externally toothed wheel, an internally toothed wheel in eccentrically disposed and in surrounding relation to said externally toothed wheel, said internally toothed wheel having a circular periphery and being rotatably disposed in said cutout, said wheels being rotatable about their respective axes to form expanding and contracting chambers, a centering device comprising a first cylindrIcal bore in said first member, a sphere having a slightly larger diameter than said first bore being press fitted into said first bore, said first bore having a depth substantially larger than the diameter of said sphere, a second cylindrical bore in said second member having a smaller diameter than said first bore and having a circular edge thereof in said plane and in contact with said sphere, and fastening means for holding said members in abutting engagement.
 2. A gear pump according to claim 1 wherein a radius from the center of said sphere to said circular edge is between 60* and 90* relative to the axis of said second bore.
 3. A gear pump according to claim 1 in which said sphere forms a pivoting point for relative pivotal movement between said members prior to said fastening means being applied.
 4. A gear pump according to claim 1 wherein said sphere is disposed on a first line which is substantially normal to a second line which extends through said axes, said first line intersecting said second line in the vicinity of said axes. 